Preparation And Application Of Stable Silane Hydrolysate

Siloxane coatings prepared from silane hydrolysates are based on Si-O-Si network structure and have the advantages of both organic and inorganic coatings.And they have been widely used in many fields in recent years.Among them,the two application scenarios of building materials waterproofing and metallic materials corrosion resisting are the current hot research fields.However,there are still many problems to be solved.For example,silane hydrolysate used in building materials generally has the disadvantages of complex preparation process and poor stability;Silane coatings applied to metallic materials are mostly applied to metal pretreatment at present,but few report about the direct application to anticorrosive coatings.So this paper has carried out the following jobs:OTES emulsion used for cement bricks was prepared from octyltriethoxysilane（OTES）as the main raw material,Span-80,Tween-20 and sodium dodecyl benzene sulfonate as the composite emulsifier.Taking the conductivity and stability of the emulsion as the measurement dimension,the influences of reaction temperature,reaction time,pH value,solid content of the emulsion and the amount of emulsifier were investigated,and the optimal process conditions were determined.It was found that the optimum conditions were the reaction temperature of 70℃,the reaction time of 5h,the pH of 11,the solid content of emulsion of 20%,and the dosage of emulsifier of 3.25wt.%.The combination of silane emulsion and substrate was characterized by measuring penetration depth,infrared spectroscopy and scanning electron microscopy,and then the capillary water absorption experiment and water contact angle experiment were carried out to characterize the coating properties.The results showed that the waterproof effect of the emulsion was ranked as follows:silica sol/Al₂O₃/OTES emulsion,silica sol/OTES emulsion and OTES emulsion.Among them,the water contact angle of silica sol/Al₂O₃/OTES coating film can reach 125.5°,and the water absorption coefficient of cement brick is 26.84 g·m^-2·h^1/2.Silane coating solution for Q235 carbon steel plate was prepared by sol-gel method with methyltrimethoxysilane（MTMS）monomer and silica sol as precursor.Firstly,the application time of the coating solution was investigated,and it was found that the viscosity and conductivity did not change much within 120h.Secondly,the corrosion resistance of the precursor coating solution with different proportions was compared by electrochemical test,and the thermal analysis was carried out.The results showed that when MTMS:silica sol=1:1,its impedance value was the highest,the polarization corrosion potential was-0.5443V,and the corrosion current was 5.274e^-6A.Thirdly,the protective properties of the coating（water contact angle and pitting corrosion test）were investigated with the reaction temperature and time,the curing temperature and time as the clue.And the optimal preparation conditions were obtained as follows:the reaction temperature was room temperature,the reaction time was 6h,and the coating was cured at room temperature for 3 days.Finally,the mechanical properties（hardness and adhesion）were investigated.Under the optimal condition,the hardness reached 5H and the adhesion reached level 1.